1. Field
This disclosure relates generally to semiconductor device packaging, and more specifically, to provide for alignment of features on a second side of a panel for double-sided processing of three-dimensional packages.
2. Related Art
As the size of electronic components becomes smaller and smaller, as does the size of devices containing those electronic components, density demands for electronic chip packaging become greater and greater. Three-dimensional packaging has emerged as a solution for achieving the higher densities of compound and necessitated by these small devices.
Through via process and double-sided processing are key elements to enable three-dimensional packages in a variety of packaging technologies (e.g., redistributed chip packaging (RCP) and flip chip packaging). After panel encapsulation, through vias can be formed by laser drilling or other techniques. The through vias are then filled with a conductor (e.g., conductive silver paste). The panel front and back sides are subsequently electrically connected using the through vias. Double-sided processing of interconnect structures can then be performed. On the side of the panel having die active surfaces, die pad contacts and other features can be used for dielectric mask alignment. On the opposite side of the panel (i.e., the panel back side), traditional methods provide only the through vias, filled with conductive silver paste or other conductive materials, as an alignment mechanism for mask alignment. But due to typically irregular through via shapes and poor contrast between via fill material and encapsulant material on the panel back side, mask alignment for back side dielectric processing is challenging.
Poor alignment of the back side processing results in decreased yields and increased costs. It is therefore desirable to have a process by which back side alignment is made more accurate, while not increasing costs due to additional equipment and process steps.
The use of the same reference symbols in different drawings indicates identical items unless otherwise noted. The figures are not necessarily drawn to scale.